Changes between Version 19 and Version 20 of Processing/SRTMDEMs


Ignore:
Timestamp:
Feb 16, 2011 4:17:23 PM (9 years ago)
Author:
knpa
Comment:

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  • Processing/SRTMDEMs

    v19 v20  
    24243. Fire up Grass. Select a location in lat/long projection using WGS84 datum (create one if none available), make a note of the selected location and mapset names.
    2525
    26 4. Import the data file:
     264. Import the data file.
     27
    2728For ASTER data:
    2829{{{
     
    3435}}}
    3536
    36 '''For multiple tiles'''
     37'''Importing and patching multiple tiles'''
    3738
    3839If the data you have downloaded spans multiple tiles, then you will need to run the above but inside a for loop like so:
     
    8990Use a conversion utility (eg see the spreadsheet at [http://www.uwgb.edu/dutchs/UsefulData/UTMFormulas.HTM#Spreadsheet http://www.uwgb.edu/dutchs/UsefulData/UTMFormulas.HTM#Spreadsheet]) to determine the boundaries of the target flight in meters within the selected UTM zone. If the flight spans two or more UTM zones, you will have to calculate the offsets appropriate to work out the east and west boundaries of the area. eg. If western boundary is zone 32 and eastern boundary is zone 33, for eastern value use zone 32, add 750000 to value from spreadsheet to find eastings relative to zone 32 bound.
    9091
    91 7. Set active region to calculated eastings/northings using
     92 - Set active region to calculated eastings/northings using
     93   {{{
     94   g.region n=<north val> s=<south val> e=<east val> w=<west val> res=50
     95   }}}
     96   For ASTER res=30
    9297
    93 {{{
    94 g.region n=<north val> s=<south val> e=<east val> w=<west val> res=50
    95 }}}
     98 - Use r.proj to convert from lat/long to UTM:
     99   {{{
     100   r.proj input=<MAP_NAME> location=<lat/long_location> mapset=<lat/long_mapset> output=<output_map_name>
     101   }}}
     102   Where <MAP_NAME> is what we created in step 4.
    96103
    97 For ASTER please put res=30
    98 
    99 8. Use r.proj to convert from lat/long to UTM:
    100 {{{
    101 r.proj input=<MAP_NAME> location=<lat/long_location> mapset=<lat/long_mapset> output=<output_map_name>
    102 }}}
    103 
    104 Where <MAP_NAME> is what we created in step 4.
    105 
    106 9. If r.proj gives an error saying that the input map is outside the bounds of the current region, go back to step 6 and check your numbers
     104 - If r.proj gives an error saying that the input map is outside the bounds of the current region, go back to step 6 and check your numbers
    107105
    108106
    109107'''Other method:'''
    110 Set the northings/eastings to something very large e.g.
    111108
    112 {{{
    113 g.region n=50000000 s=0 e=50000000 w=-50000000 res=50
    114 }}}
     109 - Set the northings/eastings to something very large e.g.
     110 {{{
     111 g.region n=50000000 s=0 e=50000000 w=-50000000 res=50
     112 }}}
     113 For ASTER res=30
    115114
    116 For ASTER please put res=30
     115 - Use r.proj to convert from lat/long to UTM:
     116 {{{
     117 r.proj input=<MAP_NAME> location=<lat/long_location> mapset=<lat/long_mapset> output=<output_map_name>
     118 }}}
     119 Where <MAP_NAME> is what we created in step 4.
    117120
    118 8. Use r.proj to convert from lat/long to UTM:
    119 {{{
    120 r.proj input=<MAP_NAME> location=<lat/long_location> mapset=<lat/long_mapset> output=<output_map_name>
    121 }}}
     121 - Set the new region
     122 {{{
     123 g.region rast=<output_map_name>
     124 }}}
    122125
    123 Where <MAP_NAME> is what we created in step 4.
    124 
    125 9.
    126 
    127 Set the new region
    128 
    129 {{{
    130 g.region rast=<output_map_name>
    131 }}}
    132 
    133 You can run
    134 
     126To run a GUI and check whether the DEM covers the correct area, or to make the area smaller, use:
    135127{{{
    136128gis.m &
    137129}}}
    138130
    139 To run a GUI and check whether the DEM covers the correct area, or to make the area smaller.
    140 
    141 10. Output ASCII DEM from converted map as normal (see [wiki:Processing/NextMapDEMs Creation of DEMs from NextMap data])
     13110. To output an ASCII DEM from the converted map, the instructions are the same as [wiki:Processing/NextMapDEMs those on the NextMap page]. Follow the instructions from about half-way down. Make sure to covert your DEM to an az-style header.
    142132
    14313311. To elevate the SRTM/ASTER DEM to the WGS84 spheroid (as is required for LiDAR deliveries and LiDAR DEM patching) see [wiki:Processing/DEM2WGS84 Elevate an SRTM/ASTER DEM to the WGS84 spheroid].
     134
     13512. When your DEM is finished, place it in ~arsf/dems and link it from within the individual projects. Make sure it's origin is contained in the file name e.g. <PROJECT_NAME>-ASTER.dem.